A Global Climate Network
The atmosphere operates as a globally connected fluid. Energy, momentum and heat are constantly exchanged across continents and oceans through large-scale circulation patterns that link distant regions of the world. Meteorologists refer to these long-range relationships as teleconnections. Rather than representing individual weather events, teleconnections describe recurring patterns of atmospheric and oceanic variability that influence regional weather far from where they originate.
The concept itself is not new. Scientists have recognised for more than a century that climate anomalies often occur simultaneously across locations separated by vast distances. Early studies of pressure fluctuations between Iceland and the Azores led to the identification of the North Atlantic Oscillation, while later research into El Niño revealed that ocean temperature anomalies off the coast of South America could influence rainfall, drought and temperature patterns across multiple continents. These discoveries fundamentally changed the understanding of the atmosphere, revealing that local weather is often embedded within a much larger planetary-scale system.
Today, teleconnections are regarded as one of the primary sources of predictability on seasonal timescales. They help explain why some winters in Europe are dominated by persistent westerly flows and Atlantic storms, while others are characterised by blocking highs, cold outbreaks and prolonged dry periods. They also provide a framework for understanding how tropical ocean variability influences weather patterns across the mid-latitudes.
Rossby Waves: The Atmospheric Messengers
The physical mechanism behind most teleconnections lies in the behaviour of planetary-scale Rossby waves. These large meanders of the jet stream act as atmospheric pathways through which disturbances can travel around the globe. When large areas of tropical convection intensify, such as during an El Niño event or an active phase of the Madden–Julian Oscillation, they release enormous quantities of latent heat into the atmosphere. This heating disrupts the atmospheric circulation and generates Rossby wave trains that propagate downstream, altering pressure patterns and jet-stream configurations thousands of kilometres away. In this way, information generated in one region of the planet can influence weather conditions in another.
The North Atlantic Oscillation and European Weather
For Europe, the most influential teleconnection is the North Atlantic Oscillation (NAO). The NAO describes fluctuations in the pressure difference between the Icelandic Low and the Azores High, two semi-permanent features of the North Atlantic circulation. Changes in this pressure gradient modify the strength and position of the North Atlantic jet stream and consequently influence storm trajectories, temperature distributions and precipitation patterns across Europe.
During a positive NAO phase, the pressure gradient strengthens, enhancing the westerly flow across the Atlantic. Storm systems are guided towards northern Europe, often bringing mild, wet and windy conditions to the British Isles, Scandinavia and parts of Central Europe. At the same time, southern Europe frequently experiences drier-than-average conditions. During a negative NAO phase, the pressure gradient weakens, allowing the jet stream to become more meandering. Blocking patterns become more frequent, increasing the likelihood of cold Arctic air reaching western and central Europe. Some of Europe's most memorable winter cold spells have occurred during strongly negative NAO episodes.
The dramatic contrast between December 2010 and the winter of 2013–2014 illustrates the influence of the North Atlantic Oscillation on European weather. December 2010 coincided with an exceptionally negative NAO phase and widespread cold conditions across much of Europe. By contrast, the winter of 2013–2014 was associated with a strongly positive NAO and one of the stormiest North Atlantic seasons on record, bringing a succession of intense Atlantic storms to northwestern Europe. The NAO alone accounts for a substantial proportion of atmospheric variability over the North Atlantic sector, making it a central component of European seasonal forecasting.
Source: NOAA / [climate.gov]
Beyond the NAO
The North Atlantic Oscillation does not act in isolation. Other teleconnection patterns can amplify or suppress its effects. The East Atlantic pattern, which shares similarities with the NAO but is displaced to the south-east, influences storm-track positioning and precipitation anomalies across western Europe. The Scandinavian pattern, characterised by pressure anomalies centred over northern Europe, often promotes blocking conditions and easterly flows when in its positive phase. Combined with a negative NAO, it can create favourable conditions for prolonged cold outbreaks across much of the continent.
El Niño, La Niña and Seasonal Predictability
Beyond the North Atlantic region, tropical Pacific variability exerts an additional influence on European weather. El Niño and La Niña events are generated through coupled ocean-atmosphere interactions in the equatorial Pacific, yet their effects can extend far beyond the tropics. During ENSO (El Niño-Southern Oscillation) events, changes in tropical convection can initiate Rossby wave trains that affect atmospheric circulation across North America and, in turn, the North Atlantic sector. Although the European response is generally weaker than in regions closer to the Pacific, ENSO can modify the probability of particular weather regimes, influence blocking frequency and affect the behaviour of the Atlantic jet stream.
Monitoring sea-surface temperature (SST) anomalies in the tropical Pacific therefore remains central to seasonal forecasting. The development of warm El Niño conditions or cool La Niña conditions often provides an early indication of potential large-scale circulation changes months in advance. These evolving SST patterns can be monitored using meteoblue seasonal forecast products, including SST anomaly maps, which help visualise regions of anomalously warm or cool ocean temperatures associated with ENSO development.
Are Teleconnections Changing?
While teleconnections have long been recognised as important drivers of climate variability, growing evidence suggests that the teleconnections themselves may be evolving in response to climate change. Traditionally, forecasting approaches assumed that relationships between large-scale climate modes and regional weather patterns remained relatively stable over time. However, recent studies have identified detectable changes in teleconnections associated with ENSO, the Indian Ocean Dipole and the Pacific Decadal Oscillation that cannot be explained by natural variability alone. Researchers suggest that changes in tropical convection, Arctic amplification, jet-stream dynamics and ocean temperature gradients may be modifying the pathways through which atmospheric signals propagate around the globe. As a result, historical teleconnection relationships may not always provide a reliable guide to future climate behaviour.
Weather in a Global Context
The complexity of teleconnections continues to challenge both climate scientists and forecasters. These patterns represent the atmosphere's long-distance communication system, linking tropical oceans, polar regions and mid-latitude weather through a network of dynamic interactions. They remind us that a weather anomaly observed in Europe may have roots far beyond the continent itself. In a climate system that operates on a planetary scale, local weather often begins as a signal originating somewhere else entirely.
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